Dynamic Call Admission Control (CAC) provides enhanced control over WAN bandwidth. When Dynamic CAC is enabled on an interface, the Branch Gateway informs the MGC of the actual bandwidth of the interface and instructs the MGC to block calls when the bandwidth is exhausted.
Dynamic CAC is especially useful in situations where a primary link is down and a backup link with less bandwidth than the primary link is active in its place. Without dynamic CAC, the MGC is unaware that the interface has switched over to the backup link. Thus, the MGC is unaware of the resulting changes in network topology and bandwidth available for the interface. Consequently, the MGC might allow calls through the interface that require more than the currently available bandwidth.
Note:
Dynamic CAC works in conjunction with the CM Call Admission Control: Bandwidth Limitation (CAC-BL) feature. A related feature is Inter-Gateway Alternate Routing (IGAR), which provides a mechanism to re-route bearer traffic from the WAN to the PSTN under certain configurable conditions. For more information on CAC-BL and IGAR, see Administrator Guide for Avaya Aura® Communication Manager.
You can enable dynamic CAC on the following interface types:
FastEthernet
GRE Tunnel
VLAN
Note:
Since VLAN interfaces are always up, configuring dynamic CAC on a VLAN interface provides a means to have a default dynamic CAC bandwidth.
